Breadcrumbs

noun: something taken as self-evident or assumed without proof as a basis for reasoning.
Mathematics, Logic. a proposition that requires no proof, being self-evident, or that is for a specific purpose assumed true, and that is used in the proof of other propositions; axiom.
a fundamental principle.
a necessary condition; prerequisite.

"The few complete specimens that have been found have 12 thorax segments. A postule in the middle of each axial ring may be present. Frontal margin perpendicular to the midline, but gradually curling backward further out. Tip blunt in frontal segments, ending in a short backward pointing spine for rear segments." Wikipedia, Dikelocephalus